1. Field of the Invention
The present invention relates to a diaphragm, the flat panel speaker, an electronic device provided with the same flat panel speaker, and a structure and method for mounting the same flat panel speaker, and more particularly to the structure and method for mounting the flat panel speaker employed in the electronic device in which the diaphragm serving also as a screen component is attached to a cabinet including an electronic device such as a foldable-type portable cellular phone using the screen component to protect a display panel as the diaphragm to emit a voice, and to the flat panel speaker used in the above structure and method, the diaphragm making up the flat panel speaker, and the electronic device in which the flat panel speaker is mounted.
2. Description of the Related Art
In recent years, due to high versatility of being usable even during movement of a user or while on a road, a portable electronic device such as a portable cellular phone is now in widespread use. Popularity has been gained by many users to a foldable and freely opening-closing type portable cellular phone, in particular, since the portable cellular phone can be housed in a compact form. Moreover, the foldable portable cellular phone becomes commercially practical which is so configured that, by using a two-axle hinge, one cabinet is allowed to freely rotate relative to another cabinet in a portion surrounding a rotational shaft mounted in a direction perpendicular to a rotational shaft used to open or close the cabinet.
In a portable cellular phone 101, as shown in FIGS. 20 and 21, an upper unit 102 and a lower unit 103 are connected to each other by a two-axle hinge 104 and, on an upper cabinet 105 of the upper unit 102 are mounted a speaker section 106 to output a received voice and a display section 107 made up of a liquid crystal display device and, on a lower cabinet 108 of the lower unit 103 are mounted an operating section 109 made up of various operational keys, a microphone section 110 to receive a transmitting voice, and a voice outputting section 111 having a speaker.
Moreover, the display section 107, as shown in FIG. 22, has a liquid crystal display panel 112 and a backlight device (not shown) to supply illuminating light to the liquid crystal display 112, all of which are held by a holding frame 113 and are housed in the upper cabinet 105. Also, a screen component 114 to protect the liquid crystal display panel 112 is bonded to a front case 115 by using a double-faced adhesive sheet 116.
The portable cellular phone 101 having, in addition to its original telephone conversation function, a data communication function of receiving and transmitting electronic mail and/or of being connected to the Internet to browse home pages is widely used. In the portable cellular phone 101 described above, for example, when a user executes a program downloaded from a site to enjoy a game, in order to hear a voice while viewing a screen of the display section 107, the portable cellular phone 101 is used with its cabinets 105, 108 opened.
However, the conventional portable cellular phone 101 has a problem. That is, when a user views a display screen of the display section 107 in a state in which the portable cellular phone 101 is folded in a compact manner with the display screen faced toward a front, the user cannot hear a voice satisfactorily since the speaker of the voice outputting section 111 hides itself. Moreover, the user, when carrying out a telephone conversation, puts the speaker section 106 on his/her ear with the cabinets 105, 108 being opened, however, since a voice hole of the speaker section 106 is comparatively small, it is difficult for the user to put the voice hole on his/her ear exactly and the portable cellular phone 101 is displaced from a position of the voice hole, as a result, causing an insufficient amount of a voice and an unclear voice. To solve this problem, in recent years, technology is proposed to be applied to a portable cellular phone (as for voice outputting from a display screen, see Non-patent reference 1: “Nikkei Business”, the Nov. 1, 2004, Nikkei Business Publication Inc., p. 90) in which, for example, a screen component used to protect a display panel of a personal computer is to be used as a diaphragm.
A flat panel speaker 201 employed in the conventional portable cellular phone 101 is mounted in a cabinet having a display section and, as shown in FIG. 23, is made of a transparent material of, for example, an acrylic resin and includes a diaphragm 202 also serving as a screen component to protect the liquid crystal display panel 112 and an actuator module 203 having a piezo-electric element which vibrates the diaphragm 202 for emission of sound waves.
The actuator module 203 is attached in a specified position of the diaphragm 202 so that vibration of the actuator module 203 is transferred to the diaphragm 202. The diaphragm 202 is attached to a front case 206 having an aperture to expose a display screen of a liquid crystal display panel in its central portion, with a frame-shaped gasket member 204 to prevent entry of foreign matter such as dust or a like being interposed between the diaphragm 202 and the front case 206 (see FIGS. 23 to 25). Here, the gasket member 204 is so configured, as shown in FIG. 25, that its inner wall face 204a surrounds the aperture of the front case 206 and is bonded, by using a frame-shaped double-faced adhesive sheet, to the diaphragm 202 and to a putting-face 206a located in the circumferential portion of the aperture of the front case 206.
To mount the flat panel speaker 201 on the cabinet of the portable cellular phone 101, as the first step, the gasket member 204 is bonded to a circumferential portion of a rear of the diaphragm 202 by using the frame-shaped double-faced adhesive sheet and the double-faced adhesive sheet is pasted to a side of the gasket member 204 placed opposite to the diaphragm 202. Next, the actuator module 203 is bonded to a specified portion of the rear of the diaphragm 202 by using, for example, a double-faced adhesive tape.
Next, the diaphragm 202 is attached to the front case 206 in a manner in which the diaphragm 202 is properly positioned relative to the front case 206 and, as shown, for example, in FIG. 20, a display screen region 202s of the diaphragm 202 is not displaced and the gasket member 204 is bonded to an edge of the aperture of the front case 206 by using a double-faced adhesive sheet. Here, as shown in FIGS. 23 to 25, a specified rectangular portion 202a (for example, rectangular portion 202a in a lower left) out of four rectangular portions 202a of the diaphragm 202 is made to strike a corresponding corner portion 206c located on an inner wall face of a side wall 206b of the front case 206 for positioning and then the gasket member 204 is bonded to the putting-face 206a of the front case 206 by using the double-faced adhesive sheet and the diaphragm 202 is attached to the front case 206 (as for technology to position a rectangular portion of a component of a device relative to a cabinet, see Japanese Patent Application Laid-open No. 2002-258249).
On a front of the holding frame 113 is fixed a liquid crystal display panel by using, for example, a frame-shaped double-faced adhesive sheet and on a rear side of the holding frame 113 is assembled to be attached a printed circuit board in a overlain state. Next, a terminal of an FPC (Flexible Printed Circuit) board is connected to a connector placed at an end of the printed circuit board. Then, a rear cover is attached from the printed circuit board side, in an assembled manner, to the holding frame 113 to which the liquid crystal display panel, light source unit, printed circuit board, or a like are attached and a component group in which the diaphragm 202, actuator module 203, gasket member 204, or a like are attached is pasted to the front case 206 and the actuator module 203 is connected to the printed circuit board via a connector. Finally, the rear cover is attached and fitted in or fastened using a fixing element such as a female (internal) screw, male (external) screw, or a like to assemble the portable cellular phone.
A problem of the conventional technology to be solved is that the cabinet of the portable cellular phone 101 comes into contact with a side surface of the diaphragm 202 over a wide range of regions and, as a result, presses a side surface of the diaphragm 202, thus causing interference with vibration of the diaphragm 202 and degradation of an acoustic characteristic of the flat panel speaker 201. That is, as shown in FIGS. 23 to 25, especially in FIG. 24, side wall faces 202m and 202n of the rectangular portion 202a of the diaphragm 202 are in contact with inner wall faces 206m and 206n of the corner portions 206c of the front case 206, respectively, in a manner to form a plane-like boundary in the contacted portion in a cross section (to form a line-like boundary when viewed from a plane side) over a wide range of the contacted region. As a result, the side surfaces of the diaphragm 202 are pressed by the front case 206, causing interference with vibration of the diaphragm 202, thus effecting adversely acoustic characteristics (in terms of degradation of voice quality and decrease in voice volume (sound level)).